COLE : VERTEBRATA FROM YUCATAN. 105 



five feet high from the level of the water to the general surface of the 

 ground. The surrounding forest crowds to the very edge of the cenote, 

 and a scanty vegetation clings to the irregularities of its walls. Tlie 

 water is fresh, is about thirty feet deep, and of a greenish color. The 

 color appears to be due to algal plankton, and not to the depth as many 

 authors have stated. The so-called Great Cenote in reality has a smaller 

 diameter at the water surface than the other, but it appears larger by 

 reason of its sloping walls. These afibrd lodgement for a vegetation 

 which maintains a luxuriant growth in consequence of the never-failing 

 supply of water. 



Tiie cenotes offer an interesting problem in connection with faunal 

 distribution. Although it is maintained by many that they are all a 

 part of a gi-eat underground river system, it seems ftiirly certain that 

 many of them are not connected with the others by definite subterra- 

 nean streams of any size, but that the general level is maintained 

 rather by " seepage " through the loose, porous rock. Our knowledge 

 of the fauna is as yet too limited to afford much evidence for either 

 view, but such as there is appears to indicate a lack of underground 

 connections of a size sufficient for fish to pass from one cenote to 

 another. This matter is more fully discussed in the introductory 

 remarks to the report on the fishes, and applies to the cenotes at 

 Chichen-Itza ; at other places, as at Izamal, there appears to be conclu- 

 sive evidence of the connection of neighboring cenotes by passages of 

 considerable size. 



Although the period of my visit fell in what is the dry season in 

 Yucatan, there was considerable rain, especially during the earlier part 

 of the time. In the latter part of February and early March, heavy 

 showers, frequently accompanied with thunder and lightning, were very 

 common in the middle of the afternoon. During this period the air was 

 usually clear, but on February 19, 20, and 21 there was a considerable 

 fog in the early morning. Except when there were showers, there was 

 nearly always a clear sky with bright sunshine ; only a few days during 

 the whole eight weeks were what could be called cloudy. In the latter 

 part of March the weather became considerably warmer and much more 

 typical of the dry season. Xearly every day there was a strong hot 

 wind which seemed to dry up everything it struck. Previously one could 

 always be comfortable when in the shade, so long as there was a breeze ; 

 now the hot wind added to one's discomforts. There was also a noticeable 

 change in the animal life, especially the insects. Certain forms which I 

 had not seen before, — such as a large species of fly which was very 



